The Die Casting Process
Die casting is a metal forming process in which molten metal is put under pressure and injected into a die. The molten metal enters the die cavity through sprue holes in the fixed die half. The melt is directed to the cavity by runners (passageways) and gates (inlets) in the ejector half. Locking pins on the die secure the two halves together. The metal, kept just above its melting temperature, quickly solidifies into the shape of the die casting. Ejector pins remove the die cast part.
Die castings are made from alloy tool steels. They have at least two sections to permit the removal of castings, the fixed die, or cover, half and the ejector die half. Some dies also have parts, such as removable slides and cores, to produce holes, threads and other desired shapes in the casting. Openings in the die allow the addition of coolant and lubricant. Dies are either air- or water-cooled. The cooling of the die provides for quick cycling and is one of the factors in the high rate of production. It also gives a fine grain structure and superior strength and finish to the metal castings. Die Casting molds can perform upwards of 5 million casts in a lifetime.
Die Casting has many advantages over other manufacturing processes. Die casting is efficient and economical, offering a wide range of durable shapes and components. Little or no machining is required after die castings are made because the process provides very close tolerances for even complex part shapes. Metal castings can be easily plated or finished. Die castings are dimensionally stable and heat resistant. These lightweight parts, even while having thin walls, retain the strength of an alloy because they do not consist of separate parts welded together.